Other than attending my nephews wedding at USD Chapel, I personally know very little about the campus vibe or academics.
-USD has a beautiful campus, a view of Mission Bay and a slightly better location than SDSU.
-Undergraduate numbers are under 6000 so a small student population.
-Catholic University
My younger son graduated from SDSU so I have more first hand experience with the campus.
Both campuses have the wonderful San Diego weather and there plenty of activities for students within and around the city but both are opposite in many ways.
-SDSU has around 30,000 undergraduates with a vibrant social vibe.
-Students are happy and active.
-Large class sizes for the required Freshman/Sophomore GE’s but upper division classes are usually under 50 students depending upon major.
-Academically challenging courses and approachable Professors
-Friendly and helpful/collaborative students
-Strong Alumni network
-San Diego Trolley station on campus which makes it easy for students with no cars to get around the city.
-Big town sports especially their Basketball team currently in the Sweet 16.
Although this discussion is comparing SDSU to UCR, you will see many posts on Why SDSU is a great option for the right student.
You might want to take a look at the Facebook parents page for both schools to get a feel for the campus culture. Since you are visiting, you can form your own opinion. ZeeMee might over better insights from the student’s prospective.
Also look over this post: http://talk.qa.collegeconfidential.com/t/weekend-student-life-at-lmu-usd-cal-poly-slo-or-sdsu/